Thermosetting resins are polymeric materials that can be observed, under the influence of heat, to irreversibly change physically, from a fusible and/or soluble polymeric material into an "intractable" (that is, an infusible and insoluble) polymeric material, through the formation of a covalently-crosslinked, generally thermally-stable polymeric network.
Various well-known thermosetting resins include phenolic and amino resins; unsaturated polyester resins; epoxy resins and polyurethanes; and silicone polymers. Other well-known thermosetting resins include alkyd resins, allyl resins, and furane resin. (See, for example, pages 436-454 and 480 of a book entitled Textbook Of Polymer Science, third edition, by Fred W. Billmeyer, Jr., published in 1984 by John Wiley & Sons, Inc.; see also pages 468-488 of the second edition of the above-identified Billmeyer text, published in 1971.)
Additionally, polyimides have recently been employed in the manufacture of certain thermosettable formulations. (See, e.g., the third edition of the above-identified Billmeyer textbook at page 428.)
It was in February of 1988, when F. Del Rector et al. (three authors in total) presented in New Orleans, La., of the United States of America, a technical paper entitled Applications For The Acetoacetyl Functionality In Thermoset Coatings. Briefly stated, these three authors reviewed some of the many, then-known methods for incorporating certain so-called "activated methylene" groups into different types or classes of resins, for purposes of preparing certain polymeric thermoset surface coatings and films, via a number of then-known crosslinking mechanisms.
More particularly, these three authors discussed various well-known methods of reacting certain acetoacetyl-functional moiety-containing polymers with certain melamines, certain isocyanates, certain aldehydes, certain diamines, and certain other specified reactants via the so-called Michael reaction, to achieve desired crosslinking of the acetoacetyl-functional moiety. For example, U.S. Pat. No. 4,408,018 to Bartman et al. notes that the reaction of acetoacetic ester with acrylic acid ester in the presence of a strong base is illustrative of the Michael reaction.
However, use of a strong base may either be undesirable or impractical. For example, current governmental regulation may impose certain substantial "use" restrictions upon such ingredients as melamines, isocyanates, and aldehydes.
Additionally, while a great many of the commonly-known polymeric thermosetting compositions are known to contain so-called aminoplasts--such as metholated melamines, isocyanates or epoxides--as crosslinking agents, there are various problems associated with certain uses of each of these crosslinking agents. For instance, the aminoplasts in general require baking conditions to effect cure; and during the baking step, aminoplasts often evolve formaldehyde or other toxic volatile products or by-products. Isocyanates, too, are known to have certain toxic effects. Further in that regard, epoxide-crosslinked systems, in general, tend to deteriorate upon being subjected to outdoor exposure. The conventionally-employed alkyd systems, moreover, are known to have relatively poor weatherability properties.
Various societal, economic and governmental pressures thus tend to mandate a non-toxic, inexpensive crosslinking system for use in the coatings industries, the textiles industries, the plastics industries, and other industries.
One of our colleagues (Richard Esser) has recently discovered that crosslinkable surface coatings can be made from polymeric compositions-of-matter or formulations that include certain acetoacetoxy-type functional pendant moieties, certain acid-functional pendant moieties and, necessarily, certain non-polymeric polyfunctional amines.
However, in the manufacture of thermosettable polymeric formulations including acetoacetoxy-type functional pendant moieties it may be desirable to avoid use of amines entirely.
Additional prior-art references, reviewed by us, that disclose various known reaction mechanisms for utilization of acetoacetoxy-type functional pendant moieties include U.S. Pat. No. 3,535,291 to Riemhofer et al.; U.S. Pat. No. 3,668,183 to Hoy et al.; U.S. Pat. Nos. 4,505,981 and 4,547,409 and 4,661,410, all to Geist; U.S. Pat. No. 4,772,680 to Noomen et al.; European Patent Application No. 0 326 723/A1 (assigned to Rohm & Haas Co.); European Pat. Application No. 0 341 886/A2 (assigned to ICI Resins BV); and European Pat. Application No. 0 390 370/A1 (assigned to Imperial Chemical Industries PL and ICI Resins BV).
Yet, in all the prior-art references reviewed by us, there is no disclosure--or even a suggestion--that the combination of acetoacetoxy-type functional pendant moieties and acid-functional pendant moieties, in the absence of crosslinking agents, might be able to be employed in the manufacture of useful thermosettable compositions.